Additive for cementitious mixtures



United States Patent O1 fice ILAHIYIINEI 3,537,869 Patented Nov. 3, 1970 3 537,869 ADDITIVE non cnlusnrmous MIXTURES Wayne A. Proell, Box 209, Seymour, Ind. 47274 No Drawing. Filed Sept. 7, 1967, Ser. No. 5,963 Int. CL C'db 13/24 US. Cl. 106-95 1 Claims ABSTRACT OF THE DISCLOSURE An additive for cementitious mixtures capable, when used in quantities in the range from 0.1% to 3.0% by weight on the cement component of the mixture, of increasing the compressive strength of the hardened product by 25% to 125%. In its optimum form, the additive consists essentially of components selected from each of three groups of organic compounds: viz, Category 1, consisting of the partial fatty acid esters of glycerol, the partial fatty acid esters of sorbitan, the partial fatty acid esters of sorbitol, the ethoxylates of the partial fatty acid esters of sorbitan, the ethoxylates of the partial fatty acid esters of sorbitol and the partial fatty acid esters of choline glycerophosphates such as are termed lecithins; Category 2, consisting of the sulfates of the partial fatty acid esters of polyglycols, the sulfate salts of the partial fatty acid esters of polyglycols, the sulfates of the partial fatty alcohol ethers of polyglycols, the sulfate salts of the partial fatty alcohol ethers of polyglycols, the sulfates of the partial fatty acid esters of glycerol and the sulfate salts of the partial fatty acid esters of glycerol; and Category 3, consisting of the sulfonated condensation products of formaldehyde and a naphthalene, and the salts of the sulfonated condensation products of formaldehyde and a naphthalene. However, certain members of Category 1 are, to a degree, effective alone, or together with each other, or with a member from either of the other categories; while members of Categories 2 and 3 are ineffective alone or in any association which does not include a member of Category I.

SPECIFICATION It is well known in the technology of concrete and related products that the strengthusually the compressive strength as measured by the ASTM test C39-64is a reliable criterion of general quality. For obvious reasons, the whole technology of concrete is developed around obtaining a significant and practical strength with a minimum of cost, and a maximum of convenience in use. Despite much research, most concrete presently used comprises a simple mixture of sand and coarse stone with a minor proportion of portland cement, sutiicient water being added to make this mixture fluid enough to place in forms. It has been known in the art that, as a general proposition, the less water used in concrete, the higher the strength; a great deal of fruitful research has occupied itself with determining what mixtures of various particle sizes of sand and stone will give fluid concrete with minimum water content. Various organic and inor ganic additives have also been tested, which permit a reduction in the water content of concrete 'while maintaining a usable level of fluidity (commonly measured in the ASTM slump test). However, these previously known additives tend to reduce strength for reasons of their chemical structure, with the result that the final strength of concretes made with such additives and lower levels of water is not increased enough'to warrant their general use; rarely is compressive strength increased more than 10%. Perhaps the most successful of such additives are various lignosulfonates, which give improvements of the concrete with respect to uniformity and workability, and often a modest enhancement in strength (generally 5l0% but occasionally up to 25%) at a very low cost. Hydroxyacids and sugars, such as tartaric acid, citric acid, and sucrose, are used to a lesser degree, the problem being that the cost of the additive and the inconvenience of measuring it (since excessive proportions of these cause deterioration of the concrete) tend to overshadow the improvement in strength, which rarely exceeds 20% in any case. The commonest organic additives are air entraining agents such as petroleum sulfonates, which are not germane to the purpose of increasing strength as these additives always reduce strength and are used to increase the resistance of concrete to frost action.

I have discovered an organic additive which, when incorporated in cementitious mixtures in a ratio of 0.1% to 3.0% on the mass of cement in the mixture, will produce strength increases on the order of 25% to 125% without significant deleterious effect upon the handling characteristics of the mixture. The additive may be mixed, in a dry state, with the cement to be used in the cementitious mixture. It may also be added to the water used in preparing the mixture, or it may be introduced into the cementitious mixture in any other manner so long as it is reasonably uniformly dispersed in the final mixture before setting occurs.

I presently believe that an optimum embodiment o my new additive should comprise at least three ingredients, including at least one selected from each of the following categories:

CATEGORY l The partial fatty acid esters of glycerol.

The partial fatty acid esters of sorbitan. The partial fatty acid esters of sorbitol.

T he ethoxylates of the rtial fatt acid esters of sot;

bitol.

The partial fatty acid esters of choline glycerophosphates such as are termed lecithins.

CATEGORY 2 The sulfates of the partial fatty acid esters of polyglycols.

The sulfate salts of the partial fatty acid esters of polyglycols.

The sulfates of the partial fatty alcohol ethers of polyglycols. I

The sulfate salts of the partial fatty alcohol ethers of polyglycols.

The sulfates of the partial fatty acid esters of glycerol.

The sulfate salts of the partial fatty acid esters 0 glycerol.

CATEGORY 3 The sulfonated condensation products of formaldehyde and a naphthalene.

The salts of the sulfonated condensation products of formaldehyde and a naphthalene.

For optimum results, I have found that a significant proportion of an ingredient from each of the above categories'must be present in the additive; and I presently believe that, although variations are permissible, as will appear hereinafter, the proportions of the several ingredients should preferably be on the order of: Category 1, 25% to 50%; Category 2, 10% to 35%; Category 3, 20% to The expression a significant proportion is used herein to distinguish from trace amounts, and may be interpreted to mean "at least about 10% by weight.

The individual substances of Categories 2 and 3 have no advantageous effects when used alone or in combination with each other but, in fact, in some instances pro duce deleterious results. Neither do the sorbitans, the sorbitols, the ethoxylates thereof, nor the partial fatty acid esters of glycerol produce any desirable effects when used :siOl'lB; but commercial, water-dispersible lecithins alone and lecithin mixed with a substance selected from Category 2 or with a substance selected from Category 3 will achieve strength enhancement on the order of 50% to 110%. Even in the case of the lecithins, the best overall propertieshigh strength, low shrinkage, and good workability-are obtained only when selected substances from each of the three categories are present.

Many of the ingredients used in these categories are .tmmercial products which need explanatory definition.

Among the ingredients which I have used is lecithin. Since the word lecithin is used rather loosely in the commercial field, I wish it to be understood that, in the present specification and in the claims appended thereto, that term, when used without qualification, is intended to include natural lecithins such as admixtures containing cephalin or lipositol as well as pure lecithin itself, and the so-called water dispersible lecithins commonly sold in comrnerce, which are hydroxylated, maleinated, ethoxylated or glycidolated derivitives of natural lecithin mixtures, or blends of natural lecithin with small amounts of dispersants. These materials are all usable for the present invention, and such commercial lecithins may otherwise be referred to as partial fatty acid esters of choline glycerophosphates.

Among the ingredients from Category 1 which I have used in the tests which are set forth in detail below are:

Commercial oil-seed lecithin which is obtainable from numerous sources on the open market.

Kelecin 1081, a product sold by the Spencer Kellogg uivision of the Textron Corporation, of Buffalo, N.Y., and which is a water dispersible lecithin believed to be an ethoxylated natural lecithin.

Centromix LP-250, a product sold by the Central Soya mnpany, of Chicago, 111., which product is a commercial ater dispersible lecithin.

Centrolene S, a product sold by the Central Soya Comnny, of Chicago, 111., which product is a hydroxylated atural lecithin.

Glycerol monostearate and glycerol monolaurate, which 1P3 commercially available from the open market in tech- 'liCal purity grades.

Atmul 84, a product sold by the Atlas Chemical Indus- ;ries, -Inc., Chemical Division, of Wilmington, Del., and hich is a mixture of approximately equal amounts of monoglycerides and the diglycerides of fatty acids from mnmon edible oils.

pan 20, a product offered for sale by the Atlas Chemi- =1. Industries, of Wilmington, Del. (formerly the Atlas wder Company) which product is a sorbitan monoirate.

Span 60, which is a sorbitan monostearate offered by same company.

Span 80, which is a sorbitan monooleate offered by ,1: same company.

Span 85, which is a sorbitan trioleate offered by the same company.

lwegp tifi, which is a pplygxyethylene sorbitan monoweate offered b the same company.

"'Arn ng t e ingredientsfrom'eategbry 2 which I have ammonium salt offered by the same company and which similar to Sipon EA, though probably differing from somewhat in the number of polyoxyethylene groups. Siponate $68, which is a lauroyl monoglyceride sulfate 4 sodium salt, ofiered by the Alcolac Chemical Corporation.

The fatty acid or fatty alcohol radicals in the substances of Categories 1 and 2 may range from 12 to 22 carbon atoms in the carbon skeleton.

Among the ingredients from Category 3 which I have used in the tests which are set forth in detail below are:

Lomar D, which is a condensate of naphthalenesulfonic acids and formaldehyde, offered by the Nopco Chemical Company, Newark, NJ.

Blancol, which is a sulfonated condensate of formaldehyde and naphthalenes, offered by the Antara Chemicals Division of General Dyestuff Corporation, New York NY.

The testing of concrete with respect to strength can be carried out with a variety of types of concrete, but usually the basic test itself is the American Society for Testing Materials C39 test. I have evaluated my present invention largely upon concrete which is a normal construction type, namely a so-called 5 bag mix with respect to contained cement, and using a crushed rock aggregate, together with a customary concrete sand (i.e., a coarse sand). However, such additives were also evaluated with high strength mixes, i.e., mixes containing 7 or 10 bags cement per cubic yard, and showed the same beneficial effects as discussed in detail below in a standard 5 bag mix. The bulk of evaluation for strength has therefore been confined to a standard 5 bag mix. On the other hand, a few test evaluations in very lean mixesso-called 3 bag mixes-showed again that such additives function beneficially in very lean mixes. I therefore present the standard five bag mix as showing typical advantages of my present invention.

The standard test concrete was made in an approximately one cubic foot charge, in a standard rotating drum contractors concrete mixer of approximately 1.5 cubic foot capacity. The ingredients were weighed out on test scales, the ratio generally used being 22 lbs. cement, 56 lbs. sand, and 84 lbs. of crushed limestone of nominal size. An initial charge of water sufficient to give a pasty mix was used, and additional water was added until an ASTM slump test of 9" plus or minus one inch was obtained. Where an additive was used, the dry additive was usually added to the initial charge of water. Thereafter cement was added, followed by the remaining ingredients. The mixer was run for 15 minutes before final water adjustment. In certain tests the order of addition was varied, with respect to time of addition of additive or water, but test results showed little significant variance in results; however, the above procedure was used in the tests reported herein to minimize variations. As mentioned before, a standard slump test and value was used to regulate the water content of the mix in order to compare concrete on a basis of practical equal fluidity. It is possible further to compare concretes of somewhat different slumps by reducing the data through slump-strength curves to the basis of exactly equal slump. In view of possible errors, the data used here is uncorrected and represents actual mixes and slumps obtained in mixes made to give as near equal slump as possible.

It will be apparent that the standard test, which uses grams of test additive per mix, constitutes the addition of 1% of additive by weight based on the portland cement used.

In each case, the concrete as mixed was cast into standard ASTM 6" x 12" compressive strength cylinders. In

most cases, the remaining concrete was cost into weathering samples (actual blocks used in an experimental retaining wall) for long term study as to soundness and weathering in practice. The test cylinders were conditioned at 100% humidity and 70 F. till set, and delivered to a commercial testing laboratory for conditioning under the same conditions for a total of 28 days, after which they were subjected to destructive compression tests by the C39 method.

The additive formulations tested were as follows:

6 Additive U-217 Percent Addltive U-2l1 Span 80 35 Percent n EA 15 Kelecin 1081 20 313: D so Lemar D 80 5 Additive -210 S an 60 40 Kelecin 1081 40 EA 24 Lomar D 60 n Lornar D 35 Additive U-209 10 Foam control agent 1 Kelccin 1081 60 Additive B-l Inmar D 40 Span 60 40 Additivc 32 Alfonic 1412A a 24 Kelecin 1081 45 Alfonic 1412A 10 Commercralioam control agent Lomm- D 45 Additive A-33 Span 60 40 Additive 0-8 Sulfate of monostearoyl polyglycol Commgrcial soybean lecithin 8O (laboratory sulfate of y i 2s Alfonic 1412s 19 D 35 Commercial foam control agent 1 Additive A-2 Atmul 84 35 Addlflve Alfonic 1412A 15 Commercial hyd'roxyiated lecithin, Centrolene S 48 25 Lonlar D 49 Lomar D 4 Foam control agent 1 Air entrainer 4 Additive A-6 Span 80 37 Addltlve Tween Centromrx LP 250 48 1 D 0 48 Foam control agent 4 4"" 4 Additive FS-31 5 Kelecin 1081 4 i Additive U 177 35 Lamar D Commercial oilseed lecithin 23 Alf i 1412s 1 gi 6412A Air entrainer 5 mar Air cntrainer 20 Span 85 Additive F848 30 Foam control agent 1 40 Ammic 1412s 34 Additive A-26 Lemar 35 Span 80 37 Commercial foam control agent i Polyoxyethylene sorbitol monolaurate 61020 24 Additive FS-60 gfii g foam control agent Commercial oil seed lecithin alone. I Additive FS-6l Additlve F543 Kelecin 1081 alone. Span 80 28 The efiects resulting from the use of the above de- Siponate SGS 28 fined formulations in tests conducted in accordance with Lomar D 30 the above explanation are set forth in the following Air entrainer 14 examples.

Compressive Percentage Additive strength, p.s.i. increme Remarks None 2, 420 0 Weathered well. Fat, pasty mix, tendency to bleed. U-2l7 3,410 41 Weatheredwell. FS-61 3,620 Harsh mix; settled. I A-2 3,645 50 Excellent workability; not harsh; placed 3,915 64 Elaine workability. 4,040 67 Medium tat mix; workability about optimm 4,085 69 Go od weatherin surfaces retained initia polish very we 1. 4,300 78 Fat, readily workable mix. 4,330 79 Good workability; thixotropic. 4, 370 81 Fair workability. 4,510 86 Harsh mix, shovelled easll good workability;wet shrinkage hi 4,610 86 Exeellentmix low wets kale. 4,540 88 Excellentworkahility. 4,720 Fair workebilityngggy mix. 7 6,010 107 Fair workability; weatherin 6, 220 Easement workabiilty; soupy in ums but Excellent workability. i) 0) Excellent workability. a I 32 Soupy, harsh mix.

Fat, thixotropie mix; excellent workability. Fat, very workable mix.

1 Tested only in laboratory micromix; laboratory evaluation showed excellent strength on qualitative basis.

Control changed inadvertently tor 0-8 mix so data not comparable ior this table. Indicated strength increase is over special control for 0-8 only.

Other additives, consisting of single substances from Category 3, single substances from Category 2, sorbitans or sorbitols alone and mixtures of substances from Category 2 with substances from Category 3, mixtures of sorbitans or glycerides with substances from Category 2, and mixtures of sorbitans or glycerides with substances from Category 3 have been tested and have been found ineffective to produce significant strength enhancement, or have actually been detrimental to strength. However, as is demonstrated by the above examples, water-dispersible lecithins alone and lecithins mixed with substances from Category 3 alone are quite effective.

While the proportions of substances selected from the three categories may be varied within a fairly wide range, as indicated above, it is quite possible by significantly exceeding the stated ranges, to destroy the beneficial effects of an additive. For example, I have found that a significant excess of a substance selected from Category 2 may result in a concrete very rich in voids and with a consequent radical reduction in strength.

It will be noted that many of the indicated examples of additives show the presence of air entrainers, foam control agents, and the like. Such agents are known in the art to be useful in producing a finished concrete, and may be used as necessary or desired in concrete containing my additives. The presence of these materials is not necessary for the present invention as is shown by such examples as FS-32, FS-3l, and U210, wherein such materials at one time assist and at another hinder maximum strength development; they are normally used for other purposes notably weathering improvement and plasticizetion.

Broadly stated, it may be said that my invention resides primarily in the discovery of additives of-the character herein disclosed which produce such significant enhancement of the strength of a given cementitious mixture that, despite the need to use relatively large amounts of the additive (0.l%3.0% is the preferred range) with consequent appreciable cost (one-half to several dollars per yard of concrete), the resultant strength increase is commercially worth while. As illustrating this, it may be pointed out that it is well known in the art that commercial additives are largely limited to sugars, hydroxyacids, and lignosulfonates because they are very cheap in the low concentrations needed for the modest benefits obtained. I use relatively expensive amounts of additives, which however, produce unusually beneficial results. Thus for a cost of one or two dollars per-cubic yard of concrete in some cases, I obtain a compressive strength which cannot readily be obtained by adding one or two dollars worth of additional cement. In fact, comparable results cannot often be obtained even with five dollars more worth of cement per cubic yard of concrete. Thus it may be said that I have broken through a barrier in reaching a level of effectiveness where one is not competing with the simple addition of more cement to a concrete mixture.

Similarly, it is well known in standard text books on concrete that strengths of 8000 or more p.s.i. can be obtained, but only with specially selected aggregates, very high cement contents, and very low slumps necessitating power compacting. Even to attain 6000 p.s.i. is difficult, and it is to be noted that the additives taught herein produce strengths up to 5220 p.s.i. in lean, "5 bag mixes, with extremely fluid mixtures of 9 inches slump. I have also shown that the same additives produce strengths of as high as 7315 p.s.i. with slump of 8%" when slightly richer 7 bag mixes are used. Comparable strengths with comparable slumps are impractical to reach in conventional concretes, as the amount of cement used is so high as to occasion unreasonable costs and impractical curing shrinkage.

Another advantage of significance, beyond mere direct material cost, lies in the amenability of the present additives to use as partial replacement for cement, in concrete to be placed in inaccessible areas where transportation or logistics costs are high. Thus, in military work, cement delivered to a combat theatre is high in cost due to the extraordinary means of transportation needed-often on human backs or by airplane-and sometimes costly in terms of lives as well as money. Its bulk, weight, and water susceptibility also increase cost. It is far more practical and less expensive to transport to a battle zone five bags of cement and five pounds of my additive, than it would be to transport the eight bags of cement which would be equivalently needed to make one yard of concrete of 5000 p.s.i. strength. Similar considerations apply to nonmilitary use in distant commercial operations, such as polar construction, mountain work, and the like, where the delivered cost of a bag of cement can be very high.

I claim as my invention:

1. A strengthening additive for cementitious mixtures, said additive consisting essentially of a significant proportion of at least one substance selected from each of Groups I, II and III, wherein Group I consists of the partial fatty acid esters of glycerol,

the partial fatty acid esters of sorbitan and ethoxylates thereof,

the partial fatty acid esters of sorbitol and ethoxylates thereof, and

the partial fatty acid esters of choline glycerophosphates such as are termed lecithins;

Group II consists of the sulfates of the partial fatty acid esters of polythe sulfate salts of the partial fatty acid esters of p a y s,

the sulfates of the partial fatty alcohol ethers of p vs y the sulfate salts of the partial fatty alcohol ethers of polyglycols,

the sulfates of the partial fatty acid esters of glycerol, and

the sulfate salts of the partial fatty acid esters of glycerol; and

Group III consists of the sulfonated condensation products of formaldehyde and a naphthalene and the salts of the sulfonated condensation products of formaldehyde and a naphthalene, the fatty acid or fatty alcohol radicals in the above sub stances ranging from about 12 to 22 carbon atoms in the carbon skeleton.

2. A strengthening additive for cementitious mixtures, said additive consisting essentially of a significant proportion of at least one substance selected from each of Groups I, II and III, wherein Group I consists of the partial fatty acid esters of choline glycerophosphates such as are termed lecithins;

Group II consists of the sulfates of the partial fatty acid esters of polythe sulfate salts of the partial fatty acid esters of p ys y the sulfates of the partial fatty alcohol ethers of polyglycols,

the sulfate salts of the partial fatty alcohol ethers of polyglycols,

the sulfates of the partial fatty acid esters of glycerol, and

the sulfate salts of the partial fatty acid esters of glycerol; and Group III consists of the sulfonated condensation products of formaldehyde and a naphthalene and the salts of the sulfonated condensation products of formaldehyde and a naphthalene, the fatty acid or fatty alcohol radicals in the above substances ranging from about 12 to 22 carbon atoms in the carbon skeleton.

3. A strengthening additive for cementitious mixtures, said additive consisting essentially'of a significant proportion of at least one substance selected from each of Groups I and II, wherein Group I consists of the partial fatty acid esters of choline glycerophosphates such as are termed lecithins; and

Group II consists of the sulfonated condensation products of formaldehyde and a naphthalene and the salts of the sulfonated condensation products of formaldehyde and a naphthalene, the fatty acid or fatty alcohol radicals in the above substances ranging from about 12 to 22 carbon atoms in the carbon skeleton.

4. A strengthening additive for cementitious mixtures, said additive consisting essentially of a significant proportion of at least one substance selected from each of Groups I, II and III, wherein Group I consists of the partial fatty acid esters of sorbitan;

Group II consists of the sulfates of the partial fatty acid esters of polyglycols,

the sulfate salts of the partial fatty acid esters of polyglycols,

the sulfates of the partial fatty alcohol ethers of polyglycols,

the sulfate salts of the partial fatty alcohol ethers of polyglycols,

the sulfates of the partial fatty acid esters of g1ycerol, and

the sulfate salts of the partial fatty acid esters of glycerol; and

Group III consists of the sulfonated condensation products of formaldehyde and a naphthalene and the salts of the sulfonated condensation products of formaldehyde and a naphthalene, the fatty acid or fatty alcohol radicals in the above substances ranging from about 12 to 22 carbon atoms in the carbon skeleton.

5. A strengthening additive for cementitious mixtures, said additive consisting essentially of a significant proportion of at least one substance selected from each of Groups I, II and III wherein Group I consists of the partial fatty acid esters of sorbitan; Group II consists of the ethoxylates of the partial fatty acid esters of sorbitan and the ethoxylates of the partial fatty acid esters of sorbitol; and

Group III consists of the sulfonated condensation products of formaldehyde and a naphthalene and the salts of the sulfonated condensation products of formaldehyde and a naphthalene, the fatty acid or fatty alcohol radicals in the above substances ranging from about 12 to 22 carbon atoms in the carbon skeleton.

6. A strengthening additive for cementitious mixtures, said additive consisting essentially of a significant proportion of at least one substance selected from each of Groups I, II and III, wherein Group I consists of the partial fatty acid esters of glycerol;

Group II consists of the sulfates of the partial fatty acid esters of poly glycols,

the sulfate salts of the partial fatty acid esters of polyglycols,

the sulfates of the partial fatty alcohol ethers of polyglycols,

10 the sulfate salts of the partial fatty alcohol ethers of polyglycols, the sulfates of the partial fatty acid esters of glycerol, and the sulfate satls of the partial fatty acid esters of glycerol; and

Group HI consists of the sulfonated condensation products of formaldehyde and a naphthalene and the salts of the sulfonated condensation products of formaldehyde and a naphthalene, the fatty acid or fatty alcohol radicals in the above substances ranging from about 12 to 22 carbon atoms in the carbon skeleton.

7. The additive of claim 1 in which the Group I substance constitutes from 25% to 50% of the total mass of the additive, the Group II substance constitutes from 10% to 35% and the Group III substance constitutes from 20% to 8. The additive of claim 2 in which the Group I substance constitutes from 20% to 30% of the total mass of additive, the Group II substance constitutes from 10% to 35% and the Group III substance constitutes from 20% to 60%.

9. The additive of claim 3 in which the Group I substance constitutes from 20% to 80%of the total mass of additive and the Group II substance constitutes from 20% to 80%. i

10. The additive of claim 4 in which the Group I substance constitutes from 25 to 40% of the total mass of additive, the Group II substance constitutes from 15% to 30% and the Group III substance constitutes from 30% 11. A concrete mixture comprising by weight parts portland cement, 20-70 parts water, 0-900 parts of a suitable aggregate, and 0.1 to 3.0 parts of an additive as defined in claim 1.

12. A concrete mixture comprising by weight 100 parts portland cement, 20-70 parts water, 0-900 parts of a suitable aggregate, and 0.1 to 3.0 parts of an additive as defined in claim 2.

13. A concrete mixture comprising by weight 100 parts portland cement, 20-70 parts water, 0-900 parts of a suitable aggregate, and 0.1 to 3.0 parts of an additive as defined in claim 3.

14. A concrete mixture comprising by weight 100 parts portland cement, 20-70 parts water, 0-900 parts of a suitable aggregate, and 0.1 to 3.0 parts of an additive as defined in claim 4.

15. A concrete mixture comprising by weight 100 parts portland cement, 20-70 parts water, 0900 parts of a suitable aggregate, and 0.1 to 3.0 parts of an additive as defined in claim 5.

16. A concrete mixture comprising by weight 100 parts portland cement, 20-70 parts water, 0-900 parts of a suitable aggregate, and 0.1 to 3.0 parts of an additive as defined in claim 6.

References Cited UNITED STATES PATENTS 2,798,003 7/ l957 Morgan et al. 106-90 2,927,033 3/1960 Benedict et al 106-90 3,008,843 11/1961 Jolly l06-95 3,145,774 8/ 1964 Patchen 106-90 3,232,777 2/ 1966 Bush 10690 3,277,162 10/1966 Johnson 106-90 TOBIAS E. LEVOW, Primary Examiner W. T. SCO'I'I, Assistant Examiner US. Cl. X.R. 

